Rename -mprefixed-addr to be -mprefixed, and document it.

Rename -mprefixed-addr to be -mprefixed, and document it.

2020-02-11  Michael Meissner  <meissner@linux.ibm.com>

	* config/rs6000/predicates.md (cint34_operand): Rename the
	-mprefixed-addr option to be -mprefixed.
	* config/rs6000/rs6000-cpus.def (ISA_FUTURE_MASKS_SERVER): Rename
	the -mprefixed-addr option to be -mprefixed.
	(OTHER_FUTURE_MASKS): Likewise.
	(POWERPC_MASKS): Likewise.
	* config/rs6000/rs6000.c (rs6000_option_override_internal): Rename
	the -mprefixed-addr option to be -mprefixed.  Change error
	messages to refer to -mprefixed.
	(num_insns_constant_gpr): Rename the -mprefixed-addr option to be
	-mprefixed.
	(rs6000_legitimate_offset_address_p): Likewise.
	(rs6000_mode_dependent_address): Likewise.
	(rs6000_opt_masks): Change the spelling of "-mprefixed-addr" to be
	"-mprefixed" for target attributes and pragmas.
	(address_to_insn_form): Rename the -mprefixed-addr option to be
	-mprefixed.
	(rs6000_adjust_insn_length): Likewise.
	* config/rs6000/rs6000.h (FINAL_PRESCAN_INSN): Rename the
	-mprefixed-addr option to be -mprefixed.
	(ASM_OUTPUT_OPCODE): Likewise.
	* config/rs6000/rs6000.md (prefixed insn attribute): Rename the
	-mprefixed-addr option to be -mprefixed.
	* config/rs6000/rs6000.opt (-mprefixed): Rename the
	-mprefixed-addr option to be prefixed.  Change the option from
	being undocumented to being documented.
	* doc/invoke.texi (RS/6000 and PowerPC Options): Document the
	-mprefixed option.  Update the -mpcrel documentation to mention
	-mprefixed.